The objective of this proposal is to produce transgenic goats by manipulation of the male germ line through male germ cell transfection and transplantation. The goats will carry the gene for human growth hormone (rhGH) under the control of a mammary gland specific promoter such that the milk of transgenic females will be an efficient source of protein for purification of human growth hormone. The milk of transgenic goats is a safe, abundant and cost effective production source for recombinant human biopharmaceuticals. GTC Biotherapeutics (formerly Genzyme Transgenics Corp.) has nearly two dozen commercial transgenic programs in development. However, even state-of-the-art methods for generating transgenic founder (first generation) goats remain relatively inefficient and expensive. Methods have been developed in rodents for transplanting genetically modified male germ cells into recipient males and mating these animals to produce transgenic offspring. During phase I of this project we successfully adapted the systems of germ cell transfection and transplantation to goats and demonstrated feasibility that recipient goats produce offspring carrying the genetic makeup of the germ cell donor animal. Now we propose to: 1) produce goats making transgenic sperm after transplantation of transfected germ cells; 2) generate transgenic embryos by in vitro fertilization and produce live transgenic offspring carrying expressing a commercially significant protein in their milk; and 3) establish a system for caprine germ cell culture to make the approach universally applicable to a wider range of transgene constructs. Successful introduction of a transgene through the male germ line will increase the efficiency and reduce the cost of generating founder animals, which is a critical early step in the transgenic production process. [unreadable] [unreadable]